Fast-growing willow shrub named ‘Millbrook’

ABSTRACT

A distinct female cultivar of  Salix purpurea×Salix miyabeana  named ‘Millbrook’, characterized by rapid stem growth producing 9% more woody biomass than one of its parents (‘SX64’) and 2% more biomass than a current production cultivar (‘SV1’). ‘Millbrook’ produced greater than 2-fold more stem biomass than two other current production cultivars, ‘SX67’ and ‘SX61’. ‘Millbrook’ can be planted from dormant stem cuttings, produces multiple stems after coppice, and the stem biomass can be harvested when the plant is dormant. In the spring following harvest, the plant will re-sprout very vigorously, producing new stems that can be harvested after two to four years of growth. This harvest cycle can be repeated several times. The stem biomass can be chipped and burned as a source of renewable energy, generating heat and/or electricity. ‘Millbrook’ displays a low incidence of rust disease.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to the following plant patent applications,all of which are subject to assignment to the Research Foundation of theState University of New York, and each of which is being filed on evendate herewith: “Fast-Growing Shrub Willow” Named ‘Fish Creek’,application Ser. No. 11/244,988, “Fast-Growing Shrub Willow” Named‘Canastota’, application Ser. No. 11/244,986, “Fast-Growing ShrubWillow” Named ‘Oneida’, application Ser. No. 11/244,975 “Fast-GrowingShrub Willow” Named ‘Otisco’, application Ser. No. 11/244,987“Fast-Growing Shrub Willow” Named ‘Owasco’, application Ser. No.11/244,842 and “Fast-Growing Shrub Willow” Named ‘Tully Champion’,application Ser. No. 11/244,635. The variety of fast-growing shrubwillow named ‘Millbrook’ was produced in the same willow breedingprogram as were other varieties, including: ‘Fish Creek’, ‘Canastota’,‘Oneida’, ‘Otisco’, ‘Owasco’, and ‘Tully Champion’.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY-SPONSOREDRESEARCH AND DEVELOPMENT

The invention described herein was reduced to practice during thefunding period of Contract 4000003235 (SUNY Research Foundation Award011275) awarded by Oak Ridge National Laboratory, managed by UT-Batellefor the United States Department of Energy under contractDE-AC05-00OR22725, and of agreement number 6267 (SUNY ResearchFoundation Award 011536) awarded by the New York State Energy Researchand Development Authority.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is a new and distinct cultivar known by the varietal name‘Millbrook’ resulting from the novel hybridization of Salix purpureawith Salix miyabeana. The new variety was produced through controlledwillow breeding conducted by the inventors in Syracuse, N.Y. Theobjective of the breeding program is to produce new willow cultivarsthat generate high biomass yields on a variety of sites, are resistantto diseases and pests, and possess agronomic traits suitable formechanical planting, harvesting, and post-harvest processing. Shrubwillow is being developed as an agricultural crop plant that will begrown and harvested as a sustainable, renewable source of energy. Once afield planting of shrub willows is established, the woody stems can beharvested every three years, and new shoots will re-sprout the followingseason. Repeated harvesting every two to four years can be sustained forat least 15 years.

2. Description of Relevant Prior Art Including Information DisclosedUnder 37 CFR 1.97-1.99.

This new variety of Salix purpurea×Salix miyabeana was the seedlingprogeny of the controlled pollination of the female clone Salix purpurea‘95026’ by the male clone Salix miyabeana ‘SX64’ performed in February1999 in Syracuse, N.Y. The plant has been propagated repeatedly by stemcuttings and has been found to retain its distinctive characteristicsthrough successive propagations and field trials. More specifically, theplant has been asexually reproduced by collecting dormant stems duringwinter months, cutting them into either 5 inch or 10 inch pieces(cuttings), then planting those cuttings in the field in the spring orin potting mix in a greenhouse, then transplanting the rooted cuttingsto the field.

The female parent, Salix purpurea ‘95026’ was originally identified in1995 growing on the shore of a creek in Dutchess County, N.Y. and wasvegetatively propagated from stem cuttings. This female parent, cloneSalix purpurea ‘95026’, is distinguished by opposite leaves that areobovate with entire margins. The variety ‘Millbrook’ has alternate‘SX64’ was originally transferred from Toronto, Ontario, Canada, toSyracuse, N.Y. in 1994 and was vegetatively propagated from stemcuttings in Syracuse, N.Y. The growth of the parent plants wascharacterized in nursery plantings. Both parents displayed rapid stemgrowth and low incidence of disease, so were chosen to serve as parentsin a cross. The seedlings produced by this cross (identification #99217)were first established in a greenhouse, and then were transplanted to afield in Syracuse, N.Y. This particular individual (identification#99217-015) was selected from the family due to its exceptional stemheight growth.

The new cultivar has been grown in Syracuse, N.Y. and Tully, N.Y., whichhave a normal yearly average daily temperature of 47° F., normal dailymaximum temperature in July of 82° F., normal daily minimum temperaturein January of 14° F., and average precipitation of 40 inches. The newcultivar grows from a rooted cutting to a fully mature plant ready forharvest in approximately three years.

SUMMARY OF THE INVENTION

The Salix purpurea×Salix miyabeana cultivar ‘Millbrook’ has not beenobserved under all possible environmental conditions. The phenotype mayvary somewhat with variations in environments such as temperature, lightintensity and length of illumination, without, however, any variation ingenotype. The new and distinct cultivar presents the following traitsthat have been repeatedly observed and are determined to be the uniquecharacteristics of ‘Millbrook’. These characteristics in combinationdistinguish ‘Millbrook’ as a new and distinct cultivar:

-   -   1. Rapid growth rate, producing 9% more woody biomass than one        of its parents (Salix miyabeana ‘SX64’), 2% more biomass than        one current production cultivar (Salix dasyclados ‘SV1’), and        more than 2-fold more biomass than two other production        cultivars (Salix miyabeana ‘SX67’ and Salix sachalinensis        ‘SX61’) when grown in the same field for the same length of time        (two growing seasons after coppice) in Tully, N.Y.    -   2. Low incidence of rust disease assessed in experimental trials        conducted in Syracuse, N.Y. in 2000.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying color photographs show the features of the claimedcultivar in a manner as true as is reasonably possible. Theillustrations include:

FIG. 1.1 illustrates two-year old portion of stem collected whiledormant;

FIG. 1.2 illustrates one-year-old portion of stem collected whiledormant;

FIG. 1.3 illustrates a vegetative bud in dormancy;

FIG. 1.4 illustrates a floral bud in dormancy;

FIG. 1.5 illustrates new shoot growth from a stem cutting rooted insoil:sand in a greenhouse;

FIG. 1.6 illustrates upper leaf surface;

FIG. 1.7 illustrates lower leaf surface;

FIG. 1.8 illustrates mature catkin; and

FIG. 1.9 illustrates pistil and densely pubescent floral bract.

FIG. 2.1 illustrates the biomass yield two years after coppice in Tully,N.Y. as compared to other shrub willows.

DETAILED DESCRIPTION OF THE NEW PLANT

The following detailed description sets forth characteristics of the newplant. The following observations and measurements describe plants grownby asexual reproduction in Syracuse, N.Y. or Tully, N.Y. underconditions as described hereinabove. Color references are made using TheRoyal Horticultural Society Colour Chart (hereinafter The R.H.S. ColourChart) of The Royal Horticultural Society of London, England, exceptwhere general terms of ordinary dictionary significance are used.

BOTANICAL DESCRIPTION OF THE PLANT

The following detailed description of the ‘Millbrook’ variety is basedon observations from 10 inch cuttings grown in a greenhouse in Syracuse,N.Y. Cuttings were grown in 7 inch tubes in a (1:1) ProMix®/sand (v/v)substrate under natural light from December 2004 to March 2005. Plantswere irrigated with automatic misting for 6 minutes every 2 hours fivetimes each day.

-   Latin name: Salix purpurea×S. miyabeana.-   Varietal denomination: ‘Millbrook’.-   Parentage:    -   -   Female or seed parent.—S. purpurea ‘95026’.        -   Male or pollen parent.—S. miyabeana ‘SX64’.-   Propagation:    -   -   Type.—Stem cuttings.        -   Time to rooting.—Approximately 10 days in water at 21° C.-   Precocity: Subprecocious — Catkins mature as leaves begin to break    bud.-   Plant description: The color of one-year-old stem cuttings observed    when dormant are grey orange (RHS 164C, RHS171A), while two- to    three-year-old stems are yellow-green to pale green (RHS 153A, RHS    148D) and lustrous. Vegetative buds are red-orange (RHS 180A),    deltate, and typically 4 mm in length. Lenticels are large, brown,    and sparse. The leaves are simple and alternate with pinnate    venation. Petioles are typically 3 mm in length and yellow-green    (151D). Stipules are typically 1 mm in length, ovate, and    yellow-green (144A). Pistils, as shown in the drawings, are    typically 1 mm in length. Immature leaves have very few hairs.    Mature leaves are slightly oblanceolate, acute apex, acute-obtuse    base, typically 8.1-8.8 cm in length, 1.5-1.9 cm in width, serrate    margin, adaxial (upper) surface green (144A), abaxial (lower)    surface light pale green (143D), and stem light green (RHS 144C) at    6 weeks of growth. The upper surface of the leaves is glabrous,    smooth, and slightly glaucous. The lower surface of the leaves is    glabrous, very light glaucous to glossy, with apparent venation.

The average diameter of two-year old stems at a height of 1 m is 1.1 cm.The bark color of two-year old field-grown stems is yellow-green (152A).The surface is slightly rough with shallow longitudinal furrows.

The average plant height of a mature plant after three seasons of growthis 5-6 m, with a spread of 1.5-2.0 m in the typical planting spacing of0.5 m×0.6 m.

-   Flowering description: Dormant floral buds are elongated, ovoid,    acute, typically 9.5 mm in length, slightly raised, and red (RHS    179A). Yellow-green (146A) peduncle of catkin is typically 3.5 mm in    length and bears 4-5 leafy bracts. Catkins are curved 90°, typically    2.6-3.0 mm in length, and narrowly cylindrical. Flowers have a    short, round, sessile ovary with short soft hairs, a very short    style, and 2 broad stigmas. Floral bract is densely hairy with a    pink obtuse apex.-   Field growth characteristics: Determined through surveys of plants    growing in the field in Tully, N.Y. and in Syracuse, N.Y.-   Disease resistance: Displays a low incidence of rust disease.-   Temperature tolerance: Stems typically do not suffer frost damage at    temperatures as low as 10° F. and may suffer only minor tip dieback    at lower temperatures.-   Seed production: ‘Millbrook’ produces only female flowers, so viable    seeds will only be produced after pollination by a compatible male    variety. This has not yet been observed in field trials.-   Biomass yield: Mean dry stem biomass yield produced through two    growing seasons after coppice in each of eight four-plant plots    (‘Millbrook’, 11.30 oven dry tons ha⁻¹ yr⁻¹) measured in a yield    trial growing in Tully, N.Y. in February 2005 was 9% greater than    the mean stem biomass yield of one of its parents (‘SX64’, 10.35    oven dry tons ha⁻¹ yr⁻¹) and was 2% greater than a current    production cultivar (‘SV1’, 11.04 oven dry tons ha⁻¹ yr⁻¹) growing    in the same trial (FIG. 2.1). ‘Millbrook’ produced greater than    2-fold more stem biomass than two other current production cultivars    (‘SX67’, 5.52 oven dry tons ha⁻¹ yr⁻¹; ‘SX61’, 4.83 oven dry tons    ha⁻¹ yr⁻¹) growing in the same trial (FIG. 2.1).

1. A new and distinct variety of Salix purpurea×Salix miyabeana plant,substantially as illustrated and described herein.